Method for manufacturing a packaged food product

ABSTRACT

A process for producing a food enclosed in sealed containers which is free from a trouble during production that water spills from the containers or a perforating jig falls into the containers and in which a heat treatment can be conducted without causing quality unevenness. A food ( 1 ) is placed in containers ( 2 ). The containers ( 2 ) filled with the food ( 1 ) are sealed with a primary film ( 4 ) having a through-hole ( 3 ) to obtain a sealed-container-packed food (A). This sealed-container-packed food (A) is disposed in a heating vessel ( 7 ) having a steam inlet part ( 5 ) and a steam discharge part ( 6 ). Steam is introduced through the steam inlet part ( 5 ) into the heating vessel ( 7 ) to heat the sealed-container-packed food (A) while discharging the steam through the steam discharge part ( 6 ). Thereafter, a secondary film ( 8 ) is bonded to each container through the primary film ( 4 ) so as to cover the through-hole ( 3 ).

TECHNICAL FIELD

The present invention relates to a method for manufacturing package-sealed rice, for example, or another packaged food product.

BACKGROUND ART

Package-sealed rice and other packaged food products are created by a process in which a single serving of rice is placed in a container and heat treated (fully cooked or half-cooked), and the container is sealed by a film.

The present applicant has filed for various patents relating to the subject of treating food products at high pressure, but because this high-pressure treatment is based on the use of hydrostatic pressure, the object treated during high-pressure treatment must be submerged, and the package must be hermetically sealed in advance.

Regardless of whether high-pressure treatment is performed, sealing the container holding the food product in advance using a film is extremely effective for preventing contamination of the container by microorganisms and the like during the transition to the next step, and preventing water and the like from spilling into the container.

However, when the container is hermetically sealed in advance in this manner, steam forms inside the sealed container due to heating when the food product is one that requires heat treatment after sealing, the internal pressure increases, and the container can break. Heat treatment is therefore performed after a steam escape hole is formed in the container (see Patent Document 1, for example).

[Patent Document 1] Japanese Laid-open Patent Application No. 2000-32965

DISCLOSURE OF THE INVENTION Problems the Invention is Intended to Solve

According to Patent Document 1, after the container that holds the food product is sealed by a film, an escape hole is formed by a hole-opening tool from above the film. However, since the hole-opening tool pushes the film downward when the hole is formed, there is a risk of water spilling into the container, or of the hole-opening tool falling into the container.

A heating press is generally used when such a container holding the food product is heated to 100° C. or higher to kill microorganisms and cook the product. A safety valve is mounted to the heating press, and the safety valve opens to release excess steam when a prescribed pressure is reached.

However, since the safety valve does not open until the inside of the heating press reaches a set pressure, the flow properties of steam inside the heating press are poor, and heat is transmitted at the start of heating from the bottom part inside the heating press, which is the part closest to the heat source (e.g., burner). Drawbacks therefore occur in that a significant temperature difference occurs with respect to the upper part inside the heating press, and uneven quality (uneven heating) occurs between products placed at the bottom of the hot press and products placed at the top of the hot press.

In view of the foregoing drawbacks, an object of the present invention is to provide an innovative method for manufacturing a packaged food product that is capable of performing heat treatment without uneven quality, and without spillage of water into the container or dropping of the hole-opening tool into the container during manufacturing.

Means for Solving these Problems

The main points of the present invention will be described with reference to the accompanying drawings.

A first aspect of the present invention relates to a method for manufacturing a packaged food product, wherein the method is characterized in comprising placing a food product 1 in a container 2, sealing the container 2 holding the food product 1 using a primary film 4 having a communicating hole 3 to obtain a packaged food product A, placing the packaged food product A inside a heating vessel 7 provided with a steam inflow part 5 and a steam discharge part 6, and causing steam to flow into the heating vessel 7 from the steam inflow part 5; and fixing a secondary film 8 so as to cover the communicating hole 3 from above the primary film 4 after heat-treating the packaged food product A while discharging the steam from the steam discharge part 6.

A second aspect of the present invention relates to the method for manufacturing a packaged food product according to the first aspect, characterized in that a heating temperature inside the heating vessel 7 is controlled by adjusting an inflow quantity of steam from the steam inflow part 5 during the heat treatment.

A third aspect of the present invention relates to the method for manufacturing a packaged food product according to the first aspect, characterized in that the packaged food product A covered by a cover body 9 is placed in the heating vessel 7, steam is allowed to flow in from the steam inflow part 5 towards the cover body 9, and heat treatment is performed.

A fourth aspect of the present invention relates to the method for manufacturing a packaged food product according to the second aspect, characterized in that the packaged food product A covered by a cover body 9 is placed in the heating vessel 7, steam is allowed to flow in from the steam inflow part 5 towards the cover body 9, and heat treatment is performed.

A fifth aspect of the present invention relates to the method for manufacturing a packaged food product according to any of the third and fourth aspects, characterized in that the packaged food product A is covered by the cover body 9 having an sloped roof 9A.

A sixth aspect of the present invention relates to the method for manufacturing a packaged food product according to any of the first through fourth aspects, characterized in that a U-shaped, V-shaped, or X-shaped cut 3 is formed in the primary film 4, and the cut 3 is used as the communicating hole 3.

A seventh aspect of the present invention relates to the method for manufacturing a packaged food product according to the fifth aspect, characterized in that a U-shaped, V-shaped, or X-shaped cut 3 is formed in the primary film 4, and the cut 3 is used as the communicating hole 3.

An eighth aspect of the present invention relates to the method for manufacturing a packaged food product according to the sixth aspect, characterized in that at the same time as the cut 3 is formed in the primary film 4 by a cutting tool in the communicating hole 3, an upward edge 3A of the cut 3 is oriented upward, or the edge 3A of the cut 3 is oriented upward after the cut 3 is formed.

A ninth aspect of the present invention relates to the method for manufacturing a packaged food product according to the seventh aspect, characterized in that at the same time as the cut is formed in the primary film 4 by a cutting tool in the communicating hole 3, an edge 3A of the cut 3 is oriented upward, or the edge 3A of the cut 3 is oriented upward after the cut 3 is formed.

A tenth aspect of the present invention relates to the method for manufacturing a packaged food product according to any of the first through fourth aspects, characterized in that a food product 1 subjected to high-pressure treatment at 1000 atmospheres or higher is placed in a container 2, the container 2 holding the food product 1 is sealed by a primary film 4 that has a communicating hole 3, and a packaged food product A is obtained.

An eleventh aspect of the present invention relates to the method for manufacturing a packaged food product according to the fifth aspect, characterized in that a food product 1 subjected to high-pressure treatment at 1000 atmospheres or higher is placed in a container 2, the container 2 holding the food product 1 is sealed by a primary film 4 that has a communicating hole 3, and a packaged food product A is obtained.

A twelfth aspect of the present invention relates to the method for manufacturing a packaged food product according to the sixth aspect, characterized in that a food product 1 subjected to high-pressure treatment at 1000 atmospheres or higher is placed in a container 2, the container 2 holding the food product 1 is sealed by a primary film 4 that has a communicating hole 3, and a packaged food product A is obtained.

A thirteenth aspect of the present invention relates to the method for manufacturing a packaged food product according to the seventh aspect, characterized in that a food product 1 subjected to high-pressure treatment at 1000 atmospheres or higher is placed in a container 2, the container 2 holding the food product 1 is sealed by a primary film 4 that has a communicating hole 3, and a packaged food product A is obtained.

A fourteenth aspect of the present invention relates to the method for manufacturing a packaged food product according to the eighth aspect, characterized in that a food product 1 subjected to high-pressure treatment at 1000 atmospheres or higher is placed in a container 2, the container 2 holding the food product 1 is sealed by a primary film 4 that has a communicating hole 3, and a packaged food product A is obtained.

A fifteenth aspect of the present invention relates to the method for manufacturing a packaged food product according to the ninth aspect, characterized in that a food product 1 subjected to high-pressure treatment at 1000 atmospheres or higher is placed in a container 2, the container 2 holding the food product 1 is sealed by a primary film 4 that has a communicating hole 3, and a packaged food product A is obtained.

EFFECTS OF THE INVENTION

The present invention as described above is an extremely practical, innovative method for manufacturing a packaged food product whereby a container holding the food product is sealed by a primary film in which a communicating hole is formed in advance, and water inside the container therefore does not spill due to downward pushing of the film by the hole-opening tool, and the hole-opening tool does not drop into the container, as in the conventional technique. The operating speed of the conveyor device in the manufacturing line can therefore be increased, and enhanced production efficiency can be anticipated. Heat treatment is not performed using an existing hot press provided with a safety valve, but a heating vessel provided with a steam inflow part and a steam discharge part is instead used in the present invention, and the packaged food product is heat treated while the steam is discharged from the steam discharge part at the same time as the steam is caused to flow into the heating vessel from the steam inflow part. Steam therefore flows satisfactorily in the heating vessel, temperature differences do not easily occur, and a substantially uniform temperature is maintained in all regions, whereby each packaged food product is heat-treated at a substantially uniform temperature even when large quantities of packaged food products are accommodated in the heating vessel and heat-treated. Products that are free of uneven quality (uneven heating) can therefore be manufactured in large quantities.

The second aspect of the present invention provides an even more practical method for manufacturing a packaged food product, wherein the heat treatment temperature can easily be adjusted by adjusting the flow rate of steam into the heating vessel, the inside of the heating vessel can be pressurized to normal pressure or higher by adjusting the flow rate of steam, and heat treatment can be performed at a temperature of 100° C. or higher, the same as in an existing hot press.

The third and fourth aspects of the present invention provide an even more practical method for manufacturing a packaged food product, wherein the packaged food product is covered by a cover body, the steam is caused to flow towards the cover body, and heat treatment is performed. Moisture (drainage) that occurs during heat treatment therefore easily adheres to the cover body, and the drainage adhering to the cover body runs off along the cover body. It is therefore difficult for the drainage to penetrate into the container from the communicating hole of the primary film.

The fifth aspect of the present invention provides an even more practical method for manufacturing a packaged food product, wherein the packaged food product is covered by a cover body having a sloped roof. It is therefore even more difficult for drainage to adhere to the primary cover of the packaged food product, and the drainage slope of the sloped roof is also set so that drainage adhering to the internal surface of the sloped roof is conducted down the internal surface, whereby a structure can easily be designed and implemented for reliably preventing drainage that adheres to the internal surface of the sloped roof from falling onto the primary cover. It is therefore even more difficult for the drainage to penetrate into the container from the communicating hole of the primary film.

In the sixth and seventh aspects of the present invention, a cut is formed in which the edge of the cut remains, and the cut is used as a communicating hole, rather than forming a round or square through-hole in the primary film. Since the presence of the edge of the cut ensures that the communicating hole is not always opened wide, it is difficult for moisture (drainage) adhering on the primary film to penetrate from the communicating hole, and the communicating hole can be obtained merely by forming a simple cut. A method for manufacturing a packaged food product can therefore be obtained that provides ease of manufacturing and even greater practicality.

The eighth and ninth aspects of the present invention provide an even more practical method for manufacturing a packaged food product, wherein the edge of the cut is oriented upward, and moisture (drainage) that occurs on the primary film during heat treatment is therefore blocked from penetrating into the cut by the upward-oriented edge. It is therefore difficult for drainage to penetrate into the container from the cut (communicating hole).

The tenth through fifteenth aspects of the present invention provide an even more practical method for manufacturing a packaged food product, wherein a good-tasting starch food product is obtained in which the degree of gelatinization is enhanced by high-pressure treatment at 1000 atmospheres or higher in a case in which the food product includes starch, for example, and a larger quantity of food products can be processed in a single high-pressure treatment than by the technique according to Patent Document 1. Such effects as enhanced production efficiency are therefore obtained.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing the packaged food product of the present example;

FIG. 2 is a front view and a side view showing a state in which the packaged food product of the present example is accommodated in the cover body;

FIG. 3 is a front view showing the heat treatment of the present example;

FIG. 4 is a front view and a side view showing a state in which the secondary film is sealed on the packaged food product of the present example; and

FIG. 5 is a perspective view showing the completed state of the packaged food product of the present example.

KEY

-   1 food product -   2 container -   3 communicating hole (cut) -   3A edge -   4 primary film -   5 steam inflow part -   6 steam discharge part -   7 heating vessel -   8 secondary film -   9 cover body -   9A sloped roof -   A packaged food product

BEST MODE FOR CARRYING OUT THE INVENTION

Preferred embodiments (the manner in which the present invention is implemented) of the present invention are briefly described below with reference to the diagrams while indicating the effects of the present invention.

A food product 1 is placed in a container 2, the container 2 holding the food product 1 is sealed by a primary film 4 in which a communicating hole 3 is provided, and a packaged food product A is obtained.

Specifically, instead of forming a hole in the film after the container holding the food product is sealed by the film as in the technique described in Patent Document 1, the container 2 holding the food product 1 is sealed by the primary film 4 in which the communicating hole 3 is formed in advance. There is therefore no spillage of water into the container, or dropping of the hole-opening tool into the container due to downward pressure on the film by the hole-opening tool.

In a common manufacturing line for this type of packaged food product A, the container is moved to the next step by a belt conveyor or other conveyor device, but the inside of the container is sometimes contaminated at this time by dust, debris, airborne bacteria, and the like in the manufacturing line, and water inside the container can be spilled by recoil of the conveyor device. Such measures as reducing the operating speed must be taken to prevent spillage. However, dust and the like can be prevented from penetrating into the container 2 by using the primary film 4 to seal the container 2, as in the present invention, and water and the like inside the container 2 does not spill even when the operating speed of the conveyor device is increased. Production efficiency can therefore be enhanced.

The packaged food product A is placed inside a heating vessel 7 provided with a steam inflow part 5 and a steam discharge part 6, steam is caused to flow into the heating vessel 7 from the steam inflow part 5, the packaged food product A is heat treated while the steam is discharged from the steam discharge part 6, and the food product 1 inside the container 2 is cooked or semi-cooked (a state in which cooking is completed by the consumer heating the product in a microwave oven or the like).

Specifically, when the inside of the heating vessel reaches the prescribed pressure, instead of heat treating using an existing hot press provided with a safety valve for releasing the steam, the packaged food product A is heat treated in the present invention while the steam is continuously discharged from the steam discharge part 6 as the steam flows into the heating vessel from the steam inflow part 5. Steam therefore flows satisfactorily in the heating vessel 7, whereby temperature differences do not easily occur inside the heating vessel 1 (*1) even at the start of heating, and a substantially uniform temperature is maintained in all regions inside the heating vessel 7. Consequently, each packaged food product A is heat-treated at a substantially uniform temperature even when large quantities of packaged food products A are accommodated in the heating vessel 7 and heat-treated. Products that are free of uneven quality (uneven heating) can therefore be manufactured in large quantities.

Steam forms inside the container 2, and the internal pressure increases due to heating at this time, but since the steam can escape to the outside of the container 2 from the communicating hole 3, the packaged food product A does not rupture during heating.

In this heat treatment, the heating temperature inside the heating vessel 7 can be controlled by adjusting the flow rate of steam from the steam inflow part 5.

Specifically, in an existing hot press, the heating temperature is determined according to the manner in which a pressure (spindle weight, spring, or screw as the safety valve) at which a safety valve operates is set. Therefore, the weight, spring, or screw must be separately adjusted according to the cooking application/purpose in order to modify the operation of the safety valve. However, in the present invention, the pressure inside the heating vessel 7 increases the more the flow rate of steam is increased using a device for forcing the inflow of steam, for example, and heat treatment can be performed at a high temperature. Conversely, the flow rate of steam may be reduced in the case of low-temperature heating, and this temperature adjustment can be easily performed. The heating vessel 7 may also, of course, be pressurized to normal pressure or higher by adjusting the flow rate of steam, heat treatment can be performed at a temperature of 100° C. or higher, the same as in an existing hot press, and it is possible to adapt to various cooking applications/purposes.

When the steam exchanges heat with the packaged food product A during this heat treatment, condensation occurs, water (drainage) forms, and the water can penetrate into the container from the communicating hole 3 and can wet the packaged food product A.

To prevent this problem, the packaged food product A is covered by a cover body 9, for example, and the flow of steam is directed towards the cover body 9 to perform the heat treatment. The drainage thereby adheres to the cover body 9 and is less likely to adhere to the packaged food product A, and it is therefore difficult for the moisture to penetrate into the container 2.

The packaged food product A is also covered by the cover body 9 having a sloped roof 9A, for example. It is therefore even more difficult for drainage to adhere to the primary cover 4 of the packaged food product A, and the drainage slope of the sloped roof 9A is also set so that drainage adhering to the internal surface of the sloped roof 9A is conducted down the internal surface, whereby a structure can easily be designed and implemented for reliably preventing drainage that adheres to the internal surface of the sloped roof 9A from falling onto the primary cover 4. It is therefore even more difficult for the drainage to penetrate into the container 2 from the communicating hole 3 of the primary film 4.

For example, moisture can be prevented from penetrating into the container 2 from the communicating hole 3 even by forming a U-shaped, V-shaped, or X-shaped cut 3 in the primary film 4 and using the cut 3 as the communicating hole 3, and orienting the edge 3A upward in the cut 3 as the communicating hole 3.

Specifically, moisture easily penetrates into the container 2 along the edge 3A when the edge 3A of the cut 3 faces downward and leads into the primary film 4. However, when the edge 3A is oriented upward, the moisture is blocked from penetrating into the cut 3 by the upward-oriented edge 3A. It is therefore difficult for moisture to penetrate into the container 2 from the cut 3.

After heat treatment is completed, the product is finished by sealing a secondary film 8 so as to cover the communicating hole 3 from above the primary film 4.

It is preferred in this finishing that the inside of the container 2 be gas-exchanged, or that an deoxidant be sealed together with the product to enhance shelf life. However, since the communicating hole 3 can be utilized as a gas introduction/discharge hole at this time, gas exchange can easily be performed, and when an deoxidant is used, the deoxidant can be prevented from being mistakenly eaten by sealing the deoxidant between the primary film 4 and the secondary film 8.

In a case in which the food product 1 includes starch, for example, a good-tasting starch food product having an enhanced degree of gelatinization is obtained by a process in which a food product 1 that is high-pressure-treated at 1000 atmospheres or higher in advance is placed in a container 2, the container 2 holding the food product 1 is sealed using a primary film 4 in which a communicating hole 3 is formed, and the packaged food product A is obtained, whereby the pressure history of the high-pressure treatment remains in the food product 1, and the aforementioned heat treatment is then performed (for a detailed description, see Japanese Patent No. 3420521 and Japanese Laid-open Patent Application No. 2000-152756).

In Japanese Laid-open Patent Application No. 2000-32965 cited as Patent Document 1, high-pressure treatment is performed after sealing rice and water in a container in advance, but when this method is used, the quantity processed in a single cycle of high-pressure treatment (the quantity of packaged food products A that can be placed in the high-pressure treatment device at once) is not large in terms of the convenience of placing each container in the high-pressure treatment device. In this regard, by sealing the food product 1 into the container 2 after performing high-pressure treatment of the food product 1 in advance, the quantity of the food product 1 that can be put in and processed is greater than when the containers 2 are placed in the high-pressure treatment device, the efficiency of each cycle of high-pressure treatment is significantly enhanced, and production efficiency is enhanced.

EXAMPLES

Examples of the present invention are described below with reference to the diagrams.

The present example is of a case in which the present invention is applied to a method for manufacturing package-sealed rice (packaged food product A) that can be heated in a microwave oven or other cooking device, in which water and uncooked rice (hereinafter referred to as uncooked rice 1) as the food product 1 are placed in an open-top shallow container 2, and a film is sealed to form a hermetic seal on the entire peripheral edge part of the open top, of the container 2.

Specifically, the container 2 holding the uncooked rice 1 and an appropriate quantity of water is sealed by the primary film 4 in which the communicating hole 3 is provided, and the packaged food product A is obtained. The “appropriate quantity” of water is a quantity of water whereby such handling problems as water improperly flowing out of the container 2 do not occur when the consumer opens the packaged food product A, and whereby a space is formed for the uncooked rice 1 to absorb the water and expand during cooking inside the container 2, and the uncooked rice 3 (*2) is satisfactorily steamed.

The communicating hole 3 is formed in advance in the primary film 4.

In the drawings, a U-shaped cut 3 is formed in two locations in the primary film 4, and each of the cuts 3 is a communicating hole 3. The cuts 3 as communicating holes 3 are cut and formed in the present example by the upward movement of a cutting tool from below the primary film 4, the edges 3A of the cuts 3 are simultaneously oriented upward so that the edges 3A do not descend below the primary film 4. The edges 3A are oriented upward so that moisture (drainage) that condenses when heat exchange between the packaged food product A and the steam is performed during the heat treatment described hereinafter does not penetrate into the container 2 from the communicating holes 3 when the drainage adheres to the packaged food product A. Specifically, a configuration is adopted in which the path of flow is changed so that drops of water flowing on the primary film 4 bypass the communicating holes 3 by coming in contact with the upward-oriented edges 3A that are provided so as to block the cuts 3, and it is difficult for the water drops to penetrate into the container 2 from the communicating holes 3.

The communicating holes 3 may also be formed by forming V-shaped or X-shaped cuts 3 in the primary film 4. Communicating holes 3 having another shape may also be formed, but the communicating holes 3 are preferably configured so as to have edges 3A for blocking the communicating holes 3 and inhibiting the entry of moisture through the communicating holes 3, and not as round or square holes that are always open.

The upward creasing of the edges 3A may be performed after the cuts are formed, and not necessarily at the same time as the cuts 3 are formed. The edges 3A of the cuts 3 may also be oriented upward after the cuts 3 are cut and formed by downward movement of the cutting tool from above the primary film 4.

It is known that the degree of gelatinization increases, and taste improves when heat treatment is performed after high-pressure treatment of the uncooked rice 1 (grain) in advance at 1000 atmospheres or higher. However, a larger quantity of the uncooked rice 1 can be accommodated, and the amount of uncooked rice 1 processed in a single cycle of high-pressure treatment increases when the uncooked rice 1 alone is stored inside the processing vessel in advance prior to be packed into the container 2, and production efficiency is enhanced when the uncooked rice 1 is subsequently packed into the container 2 relative to packing the uncooked rice 1 into the container 2 and performing high-pressure treatment for each container 2 in the treatment vessel (device), as in the technique according to Patent Document 1.

The packaged food product A is then placed in a heating vessel 7 provided with a steam inflow part 5 and a steam discharge part 6, and the packaged food product A is heat-treated while steam at a pressure of 1.0 atmosphere (absolute pressure) or higher is caused to flow into the heating vessel 7 from the steam inflow part 5, and the steam is discharged from the steam discharge part 6.

The heating vessel 7 of the present example is configured so as to have thermal insulation properties as well as pressure resistance that enables a prescribed steam pressure to be maintained, and is provided with a deck 7A inside at the bottom for mounting the packaged food product A. The heating vessel 7 and the deck 7A are preferably composed of stainless steel, for example, so as to have corrosion resistance.

The steam inflow part 5 is provided at the lower part of the heating vessel 7, and the steam discharge part 6 is provided at the upper part of the heating vessel 7.

Accordingly, a configuration is adopted in which the inside of the heating vessel 7 is heated, and the steam that flows into the heating vessel 7 from the vapor inflow part 5 at the bottom part is naturally discharged from the steam discharge part 6 at the upper part when steam is caused to flow into the heating vessel 7.

The positions of the steam inflow part 5 and the steam discharge part 6 in relation to the heating vessel 7 are not limited by the present example.

A configuration is adopted in the present example in which the pressure inside the heating vessel 7 is maintained at normal pressure or higher, and heat treatment can be performed at a temperature of 100° C. or higher.

More specifically, a configuration is adopted in which the diameter of the steam inflow vent of the steam inflow part 5 is set so as to be larger than the steam discharge vent of the steam discharge part 6, and the inside of the heating vessel 7 can be maintained at normal pressure or higher according to the difference (the inflow quantity of steam is greater than the discharge quantity) between the inflow quantity and the discharge quantity of steam as a result of the difference in vent diameters.

A temperature sensor (not shown) is provided in the vicinity of the steam discharge part 6, and the temperature of heating inside the heating vessel 7 can be controlled according to the cooking application/purpose by adjusting the inflow quantity of steam from the steam inflow part 5.

In the present example, the packaged food product A is covered by the cover body 9, and the flow of steam is directed towards the cover body 9 from the steam inflow part 5 to perform heat treatment.

More specifically, the cover body 9 has an elongated cylindrical case shape, and is configured so that a plurality of packaged food product A can be slid into the cover body 9 from the side, and heat treatment can be performed in a state in which multiple columns of cover bodies 9 are stacked in multiple levels on the deck 7A inside the heating vessel 7.

The cover body 9 is also made of a metal having good thermal conductivity, for example, and is configured so that the packaged food product A is satisfactorily heated via the cover body 9.

Consequently, through the use of the cover body 9, positioning and arrangement of the packaged food product A inside the heating vessel 7 are facilitated, this positioning can be automated using robots or the like, and excellent workability and mass production properties are obtained.

The cylindrical cover body 9 is formed so that the lower part from the middle is box-shaped in cross-section, and the upper part from the middle is wide at the bottom and shaped like a gabled roof (sloped roof 9A) in cross-section, and the cover body 9 is configured so that a collar part 2A on the periphery of the container 2 can be mounted and accommodated on a step portion 9B that occurs due to the difference in the width of the middle part of the cover body 9.

As shown in FIG. 2, the drainage slope angle θ of the sloped roof 9A of the cover body 9 is set in a range in which tan θ= 1/100 to 1.

The slope of the sloped roof 9A is set so that moisture adhering to the internal surface of the sloped roof 9A does not fall vertically, but flows down along the internal surface of the sloped roof 9A. Specifically, a configuration is adopted in which condensed moisture (drainage) adheres to the cover body 9 when the steam flowing in towards the cover body 9 from the steam inflow part 5 exchanges heat with the cover body 9, but the set slope prevents the drainage from falling onto the primary film 4 and flowing in from the communicating hole 3 even when drainage adheres to the internal surface of the sloped roof 9A.

A value of tan θ equal to 1 (45°) or higher is not preferred, because the space inside the sloped roof 9A is too wide, and the storage (placement) efficiency of the cover body 9 in the heating vessel 7 decreases.

The heat treatment can be more specifically described as pre-cooking for obtaining the manufactured product.

Two types of cooking are selected for this pre-cooking, in which the product is pre-cooked (steamed) rice that is reheated in a household microwave oven or the like, or the product is semi-cooked rice that is heated and steamed in a household microwave oven or the like. Specifically, in the case of the former type of product, the food product 1 (uncooked rice 1) is cooked to completion (steaming) by the heat treatment, and in the case of the latter type of product, the food product 1 (uncooked rice 1) is cooked to semi-completion by the heat treatment.

At this time, heat treatment is performed without closing the communicating hole 3, the communicating hole 3 is utilized as a steam escape hole for the heat treatment, and the internal pressure of the food product package 1 of the packaged food product A is prevented from increasing and rupturing the container during heat treatment.

Since this heat treatment can be performed at a temperature of 100° C. or higher by adjusting the inflow quantity of steam from the steam inflow part 5, the heat treatment can be used for various cooking purposes, sterilization purposes, and the like.

Since the inside of the heating vessel 7 can be set to and maintained (held) at a constant pressure, pressure is applied to the food product 1 (uncooked rice 1 in the present example) equally from all directions, at which time the steam as the heat source is transmitted to the food product 1 equally from all directions, and the food product 1 is therefore uniformly heated without unevenness.

In particular, since moisture included in the food product 1 does not boil under pressure, the moisture in the food product 1 does not evaporate, and advantages are gained in that the food product 1 (food) can be heat treated with no change in the moisture content or weight thereof, and the aroma component in the food product 1 is also made less likely to evaporate by the application of outside pressure.

After the heat treatment, a secondary film 8 is sealed over the primary film 4 so as to cover the communicating hole 3.

More specifically, a film having substantially the same shape as the primary film 4 is used as the secondary film 8, and the entire peripheral edge part of the back surface (lower surface) of the secondary film 8 is sealed to the entire peripheral edge part of the external surface (upper surface) of the primary film 4.

Before the secondary film 8 is sealed, the air inside the container 2 is gas-exchanged, or a deoxidant (not shown) is sealed inside to enhance shelf life.

When gas exchange is performed, the gas exchange can be performed using the communicating hole 3.

For example, since communicating holes 3 are provided in two locations of the primary film 4 in the present example, gas exchange can be performed efficiently by introducing gas to the container 2 from one of the communicating holes 3 while discharging the air inside the container 2 from the other communicating hole 3.

When a deoxidant is sealed inside, the deoxidant can be sealed in the gap between the external surface of the primary film 4 of the back surface (internal surface) of the secondary film 8. Specifically, the gap between the two films 4, 8 is communicated with the inside of the container 2 via the communicating holes 3, the deoxidizing effects can act via the communicating holes 3, and the deoxidant 6 (*3) can be sealed in the gap without the use of an adhesive.

In this case, the strength of the seal between the secondary film 8 and the primary film 4 can be set so that the primary film 4 also peels off of the container 2 together with the secondary film 8 when the secondary film 8 is peeled from the container 2 (when the upper opening part of the container 2 is opened).

In the case of a packaged food product A such as package-sealed rice, there is a risk of the deoxidant being mistaken for dried food flakes for sprinkling over cooked rice, and eaten (since the contents of the deoxidant resemble sesame and salt, the risk of mistakenly eating the deoxidant is considered to be significant in the case of cooked rice). However, a configuration is adopted in which the deoxidant is sealed between the primary film 4 and the secondary film 8 in the manner described above, and since the secondary film 8 does not separate from the primary film 4 even when the secondary film 8 is peeled away to open the container 2, the deoxidant cannot easily be removed, and the risk of mistakenly ingesting the deoxidant can be significantly reduced.

The present invention is not limited by the present example, and the specific configuration of the constituent elements may be designed as appropriate. 

1. A method for manufacturing a packaged food product, characterized in comprising: placing a food product in a container, sealing the container holding the food product using a primary film having a communicating hole to obtain a packaged food product, placing the packaged food product inside a heating vessel provided with a steam inflow part and a steam discharge part, and causing steam to flow into the heating vessel from said steam inflow part; and fixing a secondary film so as to cover said communicating hole from above said primary film after heat-treating the packaged food product while discharging the steam from said steam discharge part.
 2. The method for manufacturing a packaged food product according to claim 1, characterized in that a heating temperature inside said heating vessel is controlled by adjusting an inflow quantity of steam from said steam inflow part during said heat treatment.
 3. The method for manufacturing a packaged food product according to claim 1, characterized in that said packaged food product covered by a cover body is placed in said heating vessel, steam is allowed to flow in from said steam inflow part towards the cover body, and heat treatment is performed.
 4. The method for manufacturing a packaged food product according to claim 2, characterized in that said packaged food product covered by a cover body is placed in said heating vessel, steam is allowed to flow in from said steam inflow part towards the cover body, and heat treatment is performed.
 5. The method for manufacturing a packaged food product according to any of claims 3 and 4, characterized in that said packaged food product is covered by said cover body having a sloped roof.
 6. The method for manufacturing a packaged food product according to any of claims 1 through 4, characterized in that a U-shaped, V-shaped, or X-shaped cut is formed in said primary film, and the cut is used as said communicating hole.
 7. The method for manufacturing a packaged food product according to claim 5, characterized in that a U-shaped, V-shaped, or X-shaped cut is formed in said primary film, and the cut is used as said communicating hole.
 8. The method for manufacturing a packaged food product according to claim 6, characterized in that at the same time as said cut is formed in the primary film by a cutting tool in said communicating hole, the edge of the cut is oriented upward, or the edge of the cut is oriented upward after the cut is formed.
 9. The method for manufacturing a packaged food product according to claim 7, characterized in that at the same time as said cut is formed in the primary film by a cutting tool in said communicating hole, the edge of the cut is oriented upward, or the edge of the cut is oriented upward after the cut is formed.
 10. The method for manufacturing a packaged food product according to any of claims 1 through 4, characterized in that a food product subjected to high-pressure treatment at 1000 atmospheres or higher is placed in a container, the container holding the food product is sealed by a primary film that has a communicating hole, and a packaged food product is obtained.
 11. The method for manufacturing a packaged food product according to claim 5, characterized in that a food product subjected to high-pressure treatment at 1000 atmospheres or higher is placed in a container, the container holding the food product is sealed by a primary film that has a communicating hole, and a packaged food product is obtained.
 12. The method for manufacturing a packaged food product according to claim 6, characterized in that a food product subjected to high-pressure treatment at 1000 atmospheres or higher is placed in a container, the container holding the food product is sealed by a primary film that has a communicating hole, and a packaged food product is obtained.
 13. The method for manufacturing a packaged food product according to claim 7, characterized in that a food product subjected to high-pressure treatment at 1000 atmospheres or higher is placed in a container, the container holding the food product is sealed by a primary film that has a communicating hole, and a packaged food product is obtained.
 14. The method for manufacturing a packaged food product according to claim 8, characterized in that a food product subjected to high-pressure treatment at 1000 atmospheres or higher is placed in a container, the container holding the food product is sealed by a primary film that has a communicating hole, and a packaged food product is obtained.
 15. The method for manufacturing a packaged food product according to claim 9, characterized in that a food product subjected to high-pressure treatment at 1000 atmospheres or higher is placed in a container, the container holding the food product is sealed by a primary film that has a communicating hole, and a packaged food product is obtained. 